The invention concerns linear motion a ball bearing, comprising a housing with a generally rectangular passage for a shaft-like element having a generally rectangular cross-section. In the housing are situated at least four ball holders, each of which consists of a plate-like bearing-surface member and a cage member arranged thereon, which between them form at least one oval-shaped race for a circulating row of balls. Each raceway consists of two straight sections running parallel to one another and two curved sections connecting the ends of these straight sections. The cage member has a slot-like opening such that the balls travelling in at least one of the straight sections of the race project partially through this opening in order to come into contact with the shaft-like element, these balls being load bearing. A ball bearing of this type is known from U.S. Pat. No. 3,353,875.
In the known ball bearing each ball holder consists of a rectangular plate forming the bearing-surface member, in which is formed a longitudinal recess running through the center and, at the transverse ends of the plate, transverse recesses. In addition, on the raised sections of the plate on either side of the longitudinal recess are placed straight strips with rounded ends; these ends form the center side boundaries of the two straight race sections and the two curved sections of the two oval-shaped races formed at each plate for two circulating rows of balls. The cage member consists of a cover plate having essentially the same dimensions as the bearing-surface plate. In the surface plate are arranged two oval openings running parallel to one another at a distance apart, the boundary surfaces of which form the outer boundaries of the straight race sections and the curved sections. These side surfaces have a shape such that the circumference of the opening at the upper edge of the cage member is smaller than at the lower edge, so that the balls project slightly beyond the upper surface of this member. Four of these ball holders lie arranged loosely in a rectangle in the housing and are pressed by means of set screws against the shaft-like element. Only the rows of balls which roll over the raised sections of the bearing-surface plate are in contact with the straight side edges of the rectangular shaft.
The disadvantage of this known ball bearing is that the balls of each circulating row, on passage to the raised sections of the bearing-surface plate, must, as it were, go over a threshold, resulting in shocks. Moreover, each ball holder must have two rows of balls circulating along an oval race, while the housing and these ball holders are supplied as loose components.
The object of the invention is to provide a ball bearing of the type mentioned which does not have these disadvantages.